How much space does ext3 use?

Saturnus · 2006-01-16 23:31:13

Don't ask me why, but I used pqmagic in WinXP too create a new ext3 partition on one of my disk, and it seems like 5% of the space is used even when it's empty. Both PQmagic (in WinXP) and Kdiskfree (Arch) report this. Is this correct?

Cam · 2006-01-16 23:39:40

ext3 uses a journal so it would need to keep some space to store that.

Also, I've heard that your average linux filesystem keeps some space for /root so even on a full partition, root can still login. This could easily be a myth though, can't remember where I read that so...

pikass · 2006-01-17 10:50:48

No it is not a myth and the explanation for the "missing" space.

Saturnus · 2006-01-17 20:35:59

I switched the filesystem reiserfs (NOT reiser4), and kdiskfree shows 0,0% full. I've used reiserfs before (SuSE) and liked it, so I think I'll use reiserfs instead.

iBertus · 2006-01-17 22:11:28

By default ext3 keeps 5% free for the superuser. You can change this and make it 0% if you wish.

jakob · 2006-01-18 06:58:30

Does ext3 do that on every ext3-fs??

How can it be changed, since this function wouldn't make make sense on my 2G /home-hdd?

lucke · 2006-01-18 10:26:53

tune2fs -m 0 /dev/hdXX

TheGrudge · 2006-08-02 22:35:21

iBertus wrote:

By default ext3 keeps 5% free for the superuser. You can change this and make it 0% if you wish.

why do I need to keep space for the superuser? Is this the space for the journal? So setting this up to 0% will have to journal set to 0??

balzac · 2006-08-02 22:56:56

The space is kept for security reasons afaik (= partly for rebuilding your filesystem if the system crashes). If e.g. your root partition is full due to incredibly big log files after years, then the system will not boot at all if no space is left. With the 5% space, you can log in as root and clean the system (log files, caches etc) so that the system is useable again.

When ext3 was created, harddisks were much smaller than todays disks (maybe 500 MB big), thus 5% was not much space in those days. The drives got bigger and bigger and - of course - a value of e.g. 3% should be more than enough on todays systems. But the default setting was never changed. And there is no need to change it imho.

Insane-Boy · 2006-08-03 10:14:31

If we have 2 partitions 1 root and one which isn't with an arch do we need this "free space" for the second partition?

brain0 · 2006-08-03 14:35:08

As a rule, I set the reserved space to 0% on all data partitions and leave it at the 5% default for my root/system partition.
This can save several gigabytes on big data partitions.

twiistedkaos · 2006-08-03 23:57:30

brain0 wrote:

As a rule, I set the reserved space to 0% on all data partitions and leave it at the 5% default for my root/system partition.
This can save several gigabytes on big data partitions.

Indeed, I have done the same.

Arch Linux

#1 2006-01-16 23:31:13

How much space does ext3 use?

#2 2006-01-16 23:39:40

Re: How much space does ext3 use?

#3 2006-01-17 10:50:48

Re: How much space does ext3 use?

#4 2006-01-17 20:35:59

Re: How much space does ext3 use?

#5 2006-01-17 22:11:28

Re: How much space does ext3 use?

#6 2006-01-18 06:58:30

Re: How much space does ext3 use?

#7 2006-01-18 10:26:53

Re: How much space does ext3 use?

#8 2006-08-02 22:35:21

Re: How much space does ext3 use?

#9 2006-08-02 22:56:56

Re: How much space does ext3 use?

#10 2006-08-03 10:14:31

Re: How much space does ext3 use?

#11 2006-08-03 14:35:08

Re: How much space does ext3 use?

#12 2006-08-03 23:57:30

Re: How much space does ext3 use?

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